Drought affects soil: Learning from the world...Germany

California has suffered one on its longest droughts in recent years, so it is important to understand how our fertile agricultural regions have been affected. By understanding the stress put on the soil, we can understand more about global warming's coming impact...and how to research soil recovery in the near term to protect agricultural productivity.

Europe, too, has suffered recent droughts. They are researching how soil has been affected, and how that affects the common chemicals absorbed and cleansed by agricultural soils and natural systems.

Pesticides and soil...how do they interact after a drought?

Soils lose ability to self-clean after drought, study finds (7 September 2006)

Drought greatly reduces the natural ability of soils to degrade pesticides, a research study has found, suggesting the chemicals are more likely to accumulate as the climate becomes drier.

Scientists took the commonly used herbicide isoproturon as a 'model substance for pesticides' and studied its degradation in soils near Munich, Germany, over a period of nine years, looking closely at the effects of weather conditions on the degradation process.

While the microbial communities living in the soils degraded the herbicide very efficiently in conditions of normal humidity, the droughts of 2003 and 2006 the process had practically stopped in the top soil, the study found.

Under normal conditions, 60% of the pesticide was gone two months after being applied, but during the drought of 2003 the degradation capacity of the soil dropped dramatically.

The drought made the number of microorganisms in the soil drop and changed their composition - the bacteria that degrade isoproturon had practically disappeared from the top soil.

The effect is likely to spread as droughts become increasingly common in a warming climate. "For very badly damaged soils the deliberate introduction of suitable microorganisms might be a possibility." Dr Schroll (the head researcher) predicted.